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Reviewed CSCA Mathematics question · Easy

A circle has its center at (3, -2) and passes through the point (7, 1). What is the length of its radius?

  1. 3
  2. 4
  3. 5
  4. √7
Show the answer and explanation

Correct answer

C. 5

Principle or equation

The radius is the distance between the center and any point on the circle, calculated using the distance formula: r = √[(x2 - x1)^2 + (y2 - y1)^2].

Why this answer is correct

Using the distance formula: r = √[(7-3)^2 + (1-(-2))^2] = √[4^2 + 3^2] = √[16+9] = √25 = 5.

Example

The distance from (3, -2) to (7, 1) is 5, so the radius is 5.

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